Functionalized norbornene monomers are extensively used in the preparation of polymers having a wide variety of applications especially in the electronic industry. In particular, various electronic materials utilize polynorbornenes because of their unique film forming properties supplemented with desirable electronic material properties. Such applications include, among others, their use as dielectrics, photoresists, protective layers and liquid crystal display layers. However, as these applications require very high purity materials, it is particularly important that various functionalized norbornene monomers are free of any impurity that might make it difficult to form high molecular weight polymers.
Recently, there has been a considerable interest in the use of polynorbornene alkanol derivatives in such electronic applications as a retardation film having utility in liquid crystal displays (LCDs), see for example, PCT International Application No. WO 2008/130186.
U.S. Pat. No. 7,541,073 discloses alignment films for LCD which are made from photoreactive polymers containing polynorbornene alkanol derivatives. However, the reported yields of the monomer, norbornene methanol, is low making it unsuitable for an industrial operation. Furthermore, it is known that it is extremely difficult to make a high purity norbornene alkanol, such as, norbornene methanol having purity in excess of 95%. It is particularly difficult to prepare a norbornene alkanol in the absence of any of the corresponding hydrogenated versions, such as for example norbornane methanol. Particularly it has been reported that norbornene methanol readily undergoes hydrogenation to form norbornane methanol, see, for example, Gasanov, Russian Journal of Organic Chemistry, Vol. 39. No. 7, 2003, pp. 947-951.
It has also been reported that certain norbornene alkanol benzoates can be prepared by the reaction of dicyclopentadiene with the corresponding alkenol benzoate esters. However, the reported yields are low and use of benzoate esters in an industrial scale may not be suitable for the preparation of various norbornene alkanol derivatives, see, Guseinov et al., Doklady Akademiya Nauk Azerbaidzhanskoi SSR, 35(10), 45-8; (1979).
In view of the foregoing, there is a need to develop industrially viable processes to prepare high purity norbornene alkanol monomers.
Other objects and further scope of the applicability of the present invention will become apparent from the detailed description that follows.